However, this does not mean that the universe is lifeless other than on Earth, according to NASA.
The space agency says: ‘While no clear signs of life have ever been detected, the possibility of extraterrestrial biology – the scientific logic that supports it – has grown increasingly plausible.’
And this is not the first time scientists have said that aliens may actually be artificial intelligence. For example, British astronomer Martin Rees believes that aliens are robots that have destroyed their creators.
Lord Martin Reese, the UK’s leading astronomer royal, said aliens who may one day visit us are likely to be robots.
Numerous Hollywood films have presented the possibilities of robots becoming self-aware and deciding to destroy humans so they can rule the world.
Martin Rees, the Astronomer Royal, told Cheltenham Science Festival robots taking over was a possibility. He said: “I think if we were to detect anything artificial I think it would not be a flesh and blood civilization like ours.
“I think it will be something robotic and electronic.
“If we imagine a timeline for our Earth, it’s taken nearly four billion years for simple life to evolve into a civilisation and we’ve had technology for a few thousand years at most.
“It’s certainly on the cards that after a few centuries more – 1,000 years – we will be superseded by electronic entities.
“And they would be near-immortal and they could go on for the rest of the universe history. So they could go on for a few billion years.”